hofmann



A. vW. HOIE'MANN.

ATGHGASE DIE V Patented 011 2 1893. I

llllll UNTTED iira'rns PATENT @riucn,

ADOLPH W. HOFMANN, OF BROOKLYN, NEW YORK.

WATCHCASE-DIE.

SPECIFICATION forming part of Letters Patent No. 503,600, dated August22, 1893.

Application filed May 19, 1893. Serial No. 474,786. (No model.)

I New York, have invented certain new and use ful Improvements inWatchcase-Dies; and I do hereby declare the following to be a full,clear, and exact description of the same, reference being had to theaccompanying drawings, forming a part of this specification, and to theletters of reference marked thereon.

This invention relates to dies, such as are used in the manufacture ofwatch case backs, &c., and more especially for imparting theornamentation thereto, for which purpose the dies are suitably engravedand ornamented and the watch case backs, &c., are forced to conformthereto in a practically cold state by means of a power press or drophammer.

The objects of the invention are, first, to prevent the cracking ordistortion of the die when in use and secondly, to so construct the diesthat they may be ornamented with uniformity throughout by means of a hubor ornamented and hardened male die.

The invention consists in certain novel de tails of construction andcombinations and arrangements of parts all as will be hereinafterdescribed and pointed out particularly in the appended claims.

Referring to the accompanying drawings: Figure 1 is a sectional viewthrough a die in process of manufacture. Fig. 2 is a similar viewthrough the female die alone. Fig. 3 is a similar View with thesupporting plug in place.

Like letters of reference denote the same parts in all the views.

As is well understood by those skilled in the art, watch case backs,&c., are usually ornamented and formed by being set into female dies,which have been properly shaped, ornamented and hardenedto withstand thepressure necessary to sink the case metal into the interstices andirregularities of the die. In carrying out this method of manufacturingwatch case backs, it is found that it is difficult to secure full, sharpimpressions at the center of the die, and further, the greatestdifficulty is experienced in preventing the cracking of the die andsinking of central part.

The first difficulty mentioned, 2'. e., the failure to secure sharpimpressions at the center, I have found is due to the fact that thesteel of the female die, or die block, lettered A in the drawings, issoft when the ornamentation is'imparted thereto from the hardened andornamented male die 13, and hence, the metal of the die A gives oryields at the center sufficiently to prevent a full and sharp impressionbeing imparted thereto, producing a defective die from which it isimpossible to secure perfectly ornamented watch case backs. The seconddifliculty, is due to the fact that the solid metal of the female diecan only be successfully hardened for a comparatively short depth ordistance inward, the result of which is, that the die while perfect onthe exterior, has a soft interior, incapable of supporting the exteriorso as to make it capable of withstanding blows or the excessive pressureto which dies of this kind are subjected, and hence, when the watch casebacks are set into the ornamented concavity C and the pressure exceedsthat which can be sustained by the comparatively thin hardened exterior,the surface of the die is cracked and the center of the ornamentedsurface sinks because of the failure of the center to support the same.

Now, I have overcome the diificulties above mentioned, completely, byforming the female die with a comparatively thin body of metal as abacking for the ornamented recess, preferably, by hollowing out the dieblock A on the rear side as at D, Fig. 2, up to a point comparativelynear tho bottom of the ornamented recess, and adapting such hollowed outportion for the reception of a hardened steel plug E which whileremovable, nevertheless fits accurately in place and preferably projectsslightly below the bottom of the block at E so as to sustain the entirepressure. The diameter of the plug should conform quite accurately tothe diameter of the ornamented recess and in the preferred constructionIform shoulders e to distribute the pressure on the die block moreevenly.

In manufacturing the die, it is first formed as last described ready tobe ornamented. Then the plug having been put in place the hardened hubor ornamented male die is forced into the concavity at the top. Themetal of the die block being solidly supported by the plug will receivea uniform anrlsharp impression throughout. Then the die block is removedand hardened, the comparatively thin body of metal back of theornamented concavity being readily hardened way through, and when backedby the solid hardened steel plug is capable of withstanding Ipractically any pressure which it will be found necessary to'use even inthe manufacture of backs from hard metal.

Practical use of die blocks constructed in accordance with thisinvention, shows that the impressions given the watch case backs, aresharper, more uniform and more easily fornied than with the old forms ofdie block, and further, the blocks do not crack or sink under excessivepressure or under the action of successive blows such as are necessarytoset the watch ease backs into the die p'r'operly,

. Having thus described my invention, what I cla m as new is 1. In a diefor manufacturing watch case for the reception of the watch case back,andthe recess in'the. bottom extending up into proiiiihity to theconcavity in the top, of the hardened plug fitting in said recessandprojecti gbelow the bottom (it the die; block; substantially asdescribed. 7

ADoLPH HOFMANN.

Witnesses: H

NErH, Q- IGNA'rz MARTIN.

